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To: qemu-devel@nongnu.org
Cc: qemu-stable@nongnu.org, Christian Schoenebeck <qemu_oss@crudebyte.com>,
Greg Kurz <groug@kaod.org>, Michael Tokarev <mjt@tls.msk.ru>
Subject: [Stable-7.2.16 13/31] 9pfs: fix 'Tgetattr' after unlink
Date: Tue, 28 Jan 2025 00:41:05 +0300
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From: Michael Tokarev <mjt@tls.msk.ru>
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With a valid file ID (FID) of an open file, it should be possible to send
a 'Tgettattr' 9p request and successfully receive a 'Rgetattr' response,
even if the file has been removed in the meantime. Currently this would
fail with ENOENT.
I.e. this fixes the following misbehaviour with a 9p Linux client:
open("/home/tst/filename", O_RDWR|O_CREAT|O_EXCL, 0600) =3D 3
unlink("/home/tst/filename") =3D 0
fstat(3, 0x23aa1a8) =3D -1 ENOENT (No such file or directory)
Expected results:
open("/home/tst/filename", O_RDWR|O_CREAT|O_EXCL, 0600) =3D 3
unlink("/home/tst/filename") =3D 0
fstat(3, {st_mode=3DS_IFREG|0600, st_size=3D0, ...}) =3D 0
This is because 9p server is always using a path name based lstat() call
which fails as soon as the file got removed. So to fix this, use fstat()
whenever we have an open file descriptor already.
Fixes: 00ede4c2529b ("virtio-9p: getattr server implementation...")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/103
Signed-off-by: Christian Schoenebeck <qemu_oss@crudebyte.com>
Reviewed-by: Greg Kurz <groug@kaod.org>
Message-Id: <4c41ad47f449a5cc8bfa9285743e029080d5f324.1732465720.git.qemu_o=
ss@crudebyte.com>
(cherry picked from commit c81e7219e0736f80bfd3553676a19e2992cff41d)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
index cfe90f63cb..d950ad6de6 100644
--- a/hw/9pfs/9p.c
+++ b/hw/9pfs/9p.c
@@ -1605,7 +1605,13 @@ static void coroutine_fn v9fs_getattr(void *opaque)
retval =3D -ENOENT;
goto out_nofid;
}
- retval =3D v9fs_co_lstat(pdu, &fidp->path, &stbuf);
+ if ((fidp->fid_type =3D=3D P9_FID_FILE && fidp->fs.fd !=3D -1) ||
+ (fidp->fid_type =3D=3D P9_FID_DIR && fidp->fs.dir.stream))
+ {
+ retval =3D v9fs_co_fstat(pdu, fidp, &stbuf);
+ } else {
+ retval =3D v9fs_co_lstat(pdu, &fidp->path, &stbuf);
+ }
if (retval < 0) {
goto out;
}
--=20
2.39.5